When the dialogue box for Group Selection is not large enough to display all of the groups, you get two sliders. This makes absolutely no sense to me. I reported it as a bug back in 2012 and again early this year, yet it still behaves that way. Obviously, you folks at Bentley must see some use to it but for the life of me I can't. Why are there two sliders? Here's a screen shot so you can see what I'm talking about.
Also, notice the heading that says "Show Label" with check boxes beneath it. I've clicked these off and on for the last ten years and have never seen anything change. What the heck is that for?